There are on the market a number of different delivery devices with varying degrees of automatic functions. The general trend is also that patients should be able to administer drugs and medicament by them selves, ie. without the need for trained staff to administer the drugs.
There are however a number of aspects regarding delivery devices that are to be used by non-trained persons both in view of safety, both for the user and others that may come in contact with the device, as well as in view of handling and operation.
For safety reasons many devices have been arranged with cover or protection means that are manually or automatically activated in order to protect persons from for example an injection needle, in particular after use.
Many devices are provided with enclosures such as cartridges, ampoules or syringes containing medicament in liquid form. When filling these containers with liquid a small amount of air is very often entrapped in the container, which air has to be removed before delivery. Some devices are of multi-chamber type where one component is powder and the other is liquid or two liquids or more liquids and powder chambers.
For some types of medicament enclosures and treatment schemes there is a need to deliver a precise dose, which may be less than the total amount in the enclosure. For some types of medicament the dose to be delivered is so small that it is not practically possible to provide such a small compartment in the enclosure or to provide a device that is capable of expelling the content from such a small compartment.
The above mentioned functions have been realised in a number of delivery devices with a varying degree of complexity.
European patent application No. 298 067 discloses an injection device where mixing of two components in a cartridge and the subsequent de-aeration is performed by screwing an upper and a lower part of the device. This solution requires quite a lot of manual handling by the user in order to get the device ready for injection.
EP 298 067 further discloses a dose setting feature of the device, however without any specifications regarding the manner this can be performed.
Regarding needle covers that protect the needle after use, there are many documents disclosing this feature, eg. U.S. Pat. No. 5,658,259 and EP 298 067. The majority of these devices include either rather complex mechanisms, like the former document, that makes the production of the device rather costly or manually handled needle covers, like the latter document, with the risk that the person handling the device un-intentially injures himself on the needle.
There is thus a need for a device that is easy to handle, fulfils the safety requirements that are requested for these types of devices and is uncomplicated and can be manufactured at a reduced cost.